Reference equation for maximal heart rate in pediatric endurance athletes - REMAP Study

Abstract Background Maximal heart rate (HRmax) is used as a criterion to confirm maximal effort during cardiopulmonary exercise test (CPET) in adults and is typically age-predicted. In pediatric populations, cardiorespiratory fitness (CRF) shows an age-dependent increase. The association between demographic factors and CRF varies substantially between endurance-trained youth and their community-based counterparts. However, reference equations for age-predicted HRmax have not yet been established for pediatric endurance athletes (PEA). Purpose In this retrospective cross-sectional study, we developed a non-exercise reference equation for age-predicted HRmax tailored for PEA. Methods N=1338 healthy recreational PEA (rPEA) performed cycling CPET. N=103 (7.2%) were excluded due to submaximal effort. Maximal effort was confirmed by (1) volitional exhaustion with RPE≥8 on a 0-10 scale, (2) plateau in VO2max, and (3) RER≥1.00. N=417 girls (33.6%, age=11.5±1.2 years; BMI=18.9±3.6 kg·m-2; training experience=12.8±9.9 months) and N=824 boys (66.4%, 11.7±1.1 years-old, BMI=18.6±3.6 kg·m-2, training experience=13.8±10.3 months) fulfilled inclusion criteria. Boys had maximal oxygen uptake=50.0±8.3 mL·kg-1·min-1 and HRmax=198.5±8.1 beats·min-1, while girls had maximal oxygen uptake=44.8±7.2 mL·kg-1·min-1 and HRmax=199.7±9.0 beats·min-1. All the assumptions for linear regression were tested and found to be adequately met. Minimal multicollinearity was indicated by Variance Inflation Factor values 2. Consequently, we used multivariable stepwise linear regression to build a prediction equation based on age and other significant non-exercise demographic variables (P0.05). The accuracy of the model was reported using the coefficient of determination (R2). Results Age, sex, and weight were considered in the final model, while height, body surface area, and BMI were not included. The reference equation for HRmax in rPEA was: 200.595 + 0.409 · age (in years) – 0.158 · weight (in kg) – 1.228 · sex (girls=1, boys=2). The overall model was significant, F(3, 1237)=16.92, P0.001, but explained only 3.9% of variance (R2=0.039, adjusted R2=0.037). Age was a positive but not a significant predictor of HRmax (B=0.409, Standard Error SE=0.235, β=0.056, t=1.745, P=0.081, 95%CI −0.051, 0.869). Weight (B=-0.158, SE=0.024, β=−0.208, t=−6.508, P0.001, 95%CI -0.206, -0.110) and female sex (B=-1.228, SE=0.499, β=−0.069, t=−2.461, P=0.014, 95%CI -2.206, -0.249) were significant positive predictors of HRmax. Conclusions Contrary to the well-established relationships in the adult population, HRmax increases with age among rPEA, but age is not a significant predictor. While weight is inversely linked with HRmax in both sexes, girls exhibit a higher HRmax. Despite the limited accuracy of the presented model, it might be used to confirm maximal effort during CPET. Cross-validation in separate athletic populations and exercise modalities is warranted.Observed vs predicted maximal heart rateFor image description, please refer to the figure legend and surrounding text. Equation for maximal heart rateFor image description, please refer to the figure legend and surrounding text.